To keep pace with increasing voice, data, and video traffic, network operators have, in many areas, upgraded existing access networks by deploying optical fibers deeper into the last mile to shorten the lengths of existing copper and coaxial networks. Among different competing optical network technologies, passive optical networks (PONs) have been one of the favored choices for these next-generation access networks. With the large bandwidth of optical fibers, PONs can accommodate bandwidth-intensive voice, data, and video services.
However, the large bandwidth of PONs has increased the need to provide a high-level of network reliability. For example, because PONs have the potential to transport large amounts of data, a single faulty optical connector or fiber can interrupt a vast number of services running over the network. Therefore, network reliability is an exceedingly important issue to PON operators.
Resolving interruptions in a PON involves locating and identifying the source of the interruption. Optical time-domain reflectometry (OTDR) is often used in this capacity to locate and, potentially, identify sources of interruption, such as a fault or break in an optical fiber. OTDR is an optical measurement technique that is used to analyze the attenuation in an optical fiber (i.e., light loss). The technique specifically involves injecting a short laser pulse into an optical fiber plant and measuring the backscatter and reflection of light as a function of time. The backscattered and reflected light characteristics can then be analyzed to determine the location, for example, of any optical fiber fault/break or splice loss.
Although OTDR equipment can be used to locate and, potentially, identify sources of interruption in a PON, the effectiveness of these devices is often inhibited by noise from other devices on the PON. For example, optical network units (ONUs) attached to the PON leak optical power even when they are not transmitting. This leaking power creates noise that can affect the quality of OTDR measurements. In addition, the use of OTDR equipment often itself creates and/or necessitates interruptions in the operation of PONs.
The embodiments of the present disclosure will be described with reference to the accompanying drawings. The drawing in which an element first appears is typically indicated by the leftmost digit(s) in the corresponding reference number.